"The Obama administration believes that decisions about medical care should be made by a woman and her doctor, not a woman and her boss," Sebelius said in a statement. "We encourage the Senate to reject this cynical attempt to roll back decades of progress in women's health."

Blunt is pushing the birth-control amendment as an add-on to the transportation bill, and a vote is scheduled for Thursday.

Republicans have seized on outrage from Catholic bishops over the birth-control requirement and say the Obama administration is running roughshod over religious freedom.

The White House tried to quell the controversy by revising the mandate to allow insurers to provide birth-control directly to employees of religiously affiliated institutions, but Republicans rejected the change as sleight of hand.

Democrats argue that Blunt's proposal would go far behind the issue of contraception, and could allow any employer to reject substance abuse coverage or any other medical help that is "contrary to the provider's religious beliefs or moral convictions."

"This proposal isn't limited to contraception nor is it limited to any preventive service. Any employer could restrict access to any service they say they object to. This is dangerous and wrong," Sebelius said.